diff --git a/source/shared/core_stmt.cpp b/source/shared/core_stmt.cpp
index 51c648fe9..3b263fe22 100644
--- a/source/shared/core_stmt.cpp
+++ b/source/shared/core_stmt.cpp
@@ -1886,10 +1886,13 @@ bool convert_input_param_to_utf16( _In_ zval* input_param_z, _Inout_ zval* conve
         return true;
     }
 
-    // if the parameter is an input parameter, calc the size of the necessary buffer from the length of the string
 #ifndef _WIN32
+    // Declare wchar_size to be the largest possible number of UTF-16 characters after
+    // conversion, to avoid the performance penalty of calling ToUtf16
     wchar_size = buffer_len;
 #else
+    // Calculate the size of the necessary buffer from the length of the string - 
+    // no performance penalty because MultiByteToWidechar is highly optimised
     wchar_size = MultiByteToWideChar( CP_UTF8, MB_ERR_INVALID_CHARS, reinterpret_cast<LPCSTR>( buffer ), static_cast<int>( buffer_len ), NULL, 0 );
 #endif // !_WIN32
 
@@ -1901,15 +1904,15 @@ bool convert_input_param_to_utf16( _In_ zval* input_param_z, _Inout_ zval* conve
     wbuffer = reinterpret_cast<SQLWCHAR*>( sqlsrv_malloc( (wchar_size + 1) * sizeof( SQLWCHAR ) ));
     // convert the utf-8 string to a wchar string in the new buffer
 #ifndef _WIN32
-    int r = SystemLocale::ToUtf16Strict( CP_UTF8, reinterpret_cast<LPCSTR>( buffer ), static_cast<int>( buffer_len ), wbuffer, wchar_size );
+    int rc = SystemLocale::ToUtf16Strict( CP_UTF8, reinterpret_cast<LPCSTR>( buffer ), static_cast<int>( buffer_len ), wbuffer, wchar_size );
 #else
-    int r = MultiByteToWideChar( CP_UTF8, MB_ERR_INVALID_CHARS, reinterpret_cast<LPCSTR>( buffer ), static_cast<int>( buffer_len ), wbuffer, wchar_size );
+    int rc = MultiByteToWideChar( CP_UTF8, MB_ERR_INVALID_CHARS, reinterpret_cast<LPCSTR>( buffer ), static_cast<int>( buffer_len ), wbuffer, wchar_size );
 #endif // !_WIN32
     // if there was a problem converting the string, then free the memory and return false
-    if( r == 0 ) {
+    if( rc == 0 ) {
         return false;
     }
-    wchar_size = r;
+    wchar_size = rc;
 
     // null terminate the string, set the size within the zval, and return success
     wbuffer[ wchar_size ] = L'\0';
diff --git a/source/shared/core_util.cpp b/source/shared/core_util.cpp
index 255f335a6..4aa2b37fd 100644
--- a/source/shared/core_util.cpp
+++ b/source/shared/core_util.cpp
@@ -127,10 +127,13 @@ bool convert_string_from_utf16( _In_ SQLSRV_ENCODING encoding, _In_reads_bytes_(
         flags = WC_ERR_INVALID_CHARS;
     }
 
-    // calculate the number of characters needed
 #ifndef _WIN32
+    // Allocate enough space to hold the largest possible number of bytes for UTF-8 conversion
+    // instead of calling FromUtf16, for performance reasons
     cchOutLen = 4*cchInLen;
 #else	
+    // Calculate the number of output bytes required - no performance hit here because
+    // WideCharToMultiByte is highly optimised
     cchOutLen = WideCharToMultiByte( encoding, flags,
                                    inString, cchInLen, 
                                    NULL, 0, NULL, NULL );
@@ -156,11 +159,10 @@ bool convert_string_from_utf16( _In_ SQLSRV_ENCODING encoding, _In_reads_bytes_(
     }
     char* newString2 = reinterpret_cast<char*>( sqlsrv_malloc( rc + 1 /* NULL char*/ ));
     memset(newString2, '\0', rc+1);
-    memcpy_s(newString2, rc+1, newString, rc+1);
+    memcpy_s(newString2, rc, newString, rc);
     sqlsrv_free( newString );
 
     *outString = newString2;
-    newString2[rc] = '\0';   // null terminate the encoded string
     cchOutLen = rc;
 
     return true;